Internal Bluetooth

I wanted to add internal bluetooth to my tablet PC, so I took a USB bluetooth dongle and shoehorned it into my tablet; adding a little control PCB to allow it to be turned on and off.

Firstly I looked at the current consumption of the dongle, as I was wondering whether to bother to add a power switch of some sort. I desoldered the USB plug with my hot air reflow tool (could have used my soldering iron, of course, but to a man with a new hammer everything looks like a nail).

I reattached the plug with wires so I could add a multimeter in series with the USB power line. 

It used about 50mA when idle! I desoldered the LED, but that only used about 10mA of course. When transmitting it went up to around 140mA. 40mA is, arguably, fairly insignificant when compared to the rest of the hardware (and 10Ah battery!), but I still found it quite offensive. A power switch was required. 

I didn't want to destroy the cosmetics by adding an external switch, so I had to make use of the existing tablet buttons. There are 9 buttons on it, but all except the wifi button do something immediately when pressed. The wifi button turns the wifi on and off, but must be held down for a few seconds. So I considered turning on the bluetooth with a tap of the wifi button, leaving the wifi-switching functionality intact. A more elegant solution, however, was to use the Fn button somehow. Pressing the function button in combination with each of the other buttons activates some secondary feature, with the exception of the power and wifi buttons. Some of these features are useful, and others can be reassigned in software, so I wanted to leave them alone. So I decided to have Fn+Wifi toggle the power to the bluetooth module. This made sense to me, because both of the radio devices would share a switch!

I knew I had an extra USB port because there is an optional docking station that includes some USB devices, so I dismantled the tablet to look for it, investigate the operation of the buttons, and find a spare space for the dongle to occupy. I carefully removed the "tamper proof" Warranty Void if Removed stickers, so that I can desolder my bluetooth mod and return it to the manufacturer if my tablet ever breaks! These stickers are easily (but slowly) removed by applying lots of petrol and very gentle peeling. I found that a hypodermic syringe full of lighter fluid (petrol, basically) and a Stanley knife blade worked well. Hypodermic needles are available for free from pharmacies (at least in the UK), so that drug addicts needn't use dirty needles. They even supply sterile citric acid and spoon-replacements for safely cooking up your heroin!

Nicely tampered with, but with none of the "void void void" intruder detection! I stuck them onto some sticker backing material. My tablet had been dismantled once before, and I had done the same thing. It developed a fault and I sent it back, stickers-reattached, and Electrovaya didn't say anything! They look slightly strange in this photo, but they really are perfect.

Hunting down the USB connections was pretty tricky. Ground connections abound, of course, and a suitable 5V supply could be found by poking around likely looking chunky tracks with the multimeter in continuity mode and the other probe connected to another USB port's 5V connection. I realise that sucking power from another port isn't ideal, but it was really the only option, short of living in some fantasy dreamworld where manufacturers are actually nice to people. The multilayer board was really far too complex to find anything by following traces. I soldered on temporary power and ground connections, and poked around the docking station connector with wires soldered to the D+ and D- pads on the BT module. This was quite intersting, it seems that USB goes into some kind of "device not working properly" mode when just the D- connection is made. Windows pops up a little box to tell you so (I appologise for my use of Windows here, but I'm really stuck with it on my tablet until someone writes some decent handwriting recognition software for Linux. I now dual boot FC6). Once the D- connection was made, I poked around with the D+ connection until the device enumerated correctly. I didn't take any photos at this stage, because poking around with the wires and clicking on things occupied quite a lot of hands. Rob helped here, thanks Rob.

Once the BT module enumerated correctly, I worked out the simplest way to turn if on and off. Breaking and making the ground connection didn't work, as the device then failed to enumerate properly when reconnected. Breaking and making the +5V rail with D+, D- and ground all connected worked reliably. I therefore needed to use a p-channel FET as the switch.

Next I hunted down the switch connections. I removed the board to see how it worked, but I didn't really need to, I should have just looked at the voltages on the connector pins.

Each button simply grounds one of the pins on the connector. They must be pulled high on the motherboard. I found the two pins responsible for the wifi and Fn buttons, and measured the signals to be 5V, and active low. So I designed a simple circuit with a dual switch debouncer to clean up the switch signals, a tiny logic NOR gate to produce the AND behaviour (because a NOR with inverted inputs is an AND), a D-type latch to generate the latching function, and a p-channel fet to do the switching. I knocked it up in eagle, and produced a little PCB layout.

The NOR gate has a funky symbol because it is actually a TI 74LVC1G57 "Multi-configurable gate", which does different things depending on which pins are connected high, low, or to other pins. I didn't have a tiny logic NOR gate to hand. Note I read the datasheet wrong, and ended up modding the PCB! The schematic is still wrong, so don't go and build it! I also drew funky hourglass symbols for the switch debouncers. Also note the RC network on the Preset pin of the 7474. It is there to set the output high just after the circuit is powered up. This way the tablet powers up with the bluetooth switched off, rather than in an undefined state. Time constant is not critical, just a few ms. The pull-up on the FET is not really required, just added instinctively. Unused inputs on the other half of the 7474 are tied high. C2 and C3 are decoupling caps.

Here's the PCB layout.

I etched it by my standard photolithographic means, along side some of Xbee test adapters for Rob. I made two copies just in case.

Here's the finished board, cut out and resist-stripped, with the bluetooth adapter. Isn't it embarrasing that my ridiculously simple board is about the same size?! One day...

The sharpest readers may have noticed that's not the same bluetooth module I had at the start. The first one was too cheap to work properly in Windows. Works fine in Linux, so I reassembled it for use with my laptop.

I populated the board. See the flickr set for more details, and more on the PCB etching process too. I didn't have any solder paste, so I assembled it with a soldering iron. I did solder on a couple of components by tinning the pads and reflowing with the hot air tool because it was brand new and I wanted to know what it was like! It's worth noting that there's little you can do with a hot air tool that can't be done with more patience with a soldering iron. With the exception of BGAs, of course, and desoldering very large, fiddly things. I drilled a couple of holes to allow for wires to the existing mechanical support holes in the BT module.

I soldered the bluetooth module directly to the board. I had intended to mount the bluetooth module up the other way, but I accidentally mirrored the layout of the connector! It worked out well though, with small bits of wire bridging the solder joints (not visible, embedded in the blobs). 

I soldered on some temporary connections, and hooked it up to a breaboard to test it because, as we know, the simplest of PCBs don't work first time. The LED was connected in parallel with the BT module, to indicate it's power status. The flying wires and pullup resistors are emulating the buttons.

This, the simplest PCB in the world, didn't work first time. I had the multiconfigurable gate configured incorrectly, as described above! Kynar wire to the rescue (blue, on the left).

I replaced the chunky temporary breadboard wire with nice, thin kynar wire. I twisted the D+ and D- leads together for some noise immunity, reasoning that it would help since USB is differential. Does it help? Who knows.

Then I began soldering stuff to the motherboard. Feel the freedom of modding, comrades!

Tinning the button connections


Soldering the USB connections to the docking station connector

All the connections made, I temporarily taped it down and tested it at this stage. Sure enough, pressing Fn+Wifi resulted in a nice windowsy "pong-ping!" sound and a new hardware pop-up! Another press led to a nice "ping-pong". I neglected to photograph it, because I'm an idiot. Watch the video at the bottom instead.

I added some heatshrink, and tucked it away in a corner. I checked the corner was roomy enough first by adding a little column of blu tack, screwing the case together to squash it, and measuring its final height.

I reassembled the case, and tested the range. It was a rather disappointing 30mm or so, and only from the back of the tablet! I was both surprised and not surprised. People have done it successfully on other laptops without offering any sacrifices to the easily-angered RF gods, but it's a pretty much perfect Faraday cage!

So I decided to sacrifice my auxilliary wifi antenna and connect it to the bluetooth module in place of its weedy chip antenna.

I desoldered a UFL connector from an old wifi module (thanks Justyn!)  and added it to the BT module:


Fortunately it just fitted at that jaunty angle without my having to extend the antenna connection.

The range is now excellent - a good few metres. Wifi performance doesn't seem to have degraded noticeably. This is possibly because the antennas are orthogonally placed for use in portrait and landscape modes, and I pretty much always use my tablet portrait. Who knows, wifi is essentially witchcraft. One day I would like to add an external antenna socket to extend wifi range in times of need. Early experiments with a 7dBi antenna on a UFL pigtail seemed to improve perfomance quite impressively.

Here's a really exciting video



As per Electrical Idiot's request below, I have created an alternative, single input, schematic

It has just one switch input which toggles the power when the switch input goes high. Note that this is just one of many ways to build this circuit. The original one was made to be as compact as possible with the parts I had to hand. As long as you have something to debounce the switch (this may even be included on your laptop motherboard if you poke around), some kind of latch to toggle the power, and a P-channel FET with a fairly low Rds(on) at -5V gate-source voltage, then you're set. I like the Maxim range of debouncers, but if you can't get hold of them you could use a schmitt-RC combo, or even a small microcontroller if you really want.

Could you at least make the

Could you at least make the photo's of your work public? They all seem to be private.

cheapest boots

sales on uggs mini boots Gourmets still gently pat his shoulder. dfg32af

uggs boots for sale Gourmets gently asked: "Why come to see me?"

uggs sale cheap Him relax, "the police, not the thief?" Yinbai never happy with this sister.

Good work!

You done a really professional work! I can't see full size images because Flickr shouts: "Oops! You don't have permission to view this photo."

Flickr fixed

Oops, hadn't realised photos were private. Should be fixed now.

Thanks, maros.

Your site is good Actually,

Your site is good Actually, i have seen your post and That was very informative and very entertaining for me. quotes for everything

Needles in the USA

We have a similar program here in the states (referring to the needles) however some local Law "enforcement" have taken it upon themselves to push the blatant lie to pharmacy's that they cannot sell needles/syringes to ANYBODY for fear of the druggies coming back and robbing the stores.

This is, of course, total rubbish.

Pharmacy's have a LEGITIMATE NEED for needles--diabetics--and as such, they usually give them away for free to anybody who's either a diabetic or is getting medicine from the pharmacy that requires a syringe.

However, if you are a law-abiding citizen and (thankfully) do not have diabetes, how do you procure said needles? Most of the time, the pharmacists (nothing more than glorified candy-striper's, if you ask me) take the moral high-ground and will flat-out refuse to give you the needles, even if you want to buy them. And in other cases, they will ask you for your name and address--for what purpose, I can only guess is to give to someone to put you on a list of some sort... Nobody wants that.

There are some ways around all that:

1. Purchase them on the Internet. A quick look for "Syringe" found hundreds of hits, at very reasonable prices. You could buy quite a number of them, and they ship cheaply too.

2. Find a drugstore that isn't pressured by the local Deputy-doofus, and purchase them legally. After all, it's a DRUGSTORE--they are supposed to have them.

3. Contact a free clinic, and they will most likely give them to you. However, these are usually located where they can do the most good--and as such, are in quite seedy neighborhoods.

I am sick and tired of personal liberties being taken away from me for the supposed 'common good' and local law enforcement overstepping their boundaries and actively trying to prevent law-abiding citizens from getting things without hassle.

Stand up for your rights, but be smart about it. Don't make a scene, and have something on your side that they don't have: Knowledge. Research local laws before attempting to assert yourself. You will get a lot farther in life if you admit that you don't know things, than trying to lie about it.

vet supply

In the US, if your local pharmacy won't sell you needles, your veterinarian's office will sell them. I give all my dogs their vaccinations at home. Syringes are easy to get.


you can get some nice needles from the ink jet refill kits they sell at staples and these things are huge!!

I'm too stupid to figure this out by myself

i'm trying to do this for my own laptop.. problem is, i'm an idiot, and new to building circuits.. you said not to use the schematic you posted.. any chance you could post a corrected one for me, and with a single switch trigger instead of two? thanks -idiot


No problem, see the Update section above. Good luck!

i wussed out...

I wussed out on your "good" version of this project.. and made a much easier "crappy" version.. heh.. my laptop had 4 usb ports.. 2 on one breakout board right next to each other.. and i'll never use 4 at once.. so i popped the usb jack off of the breakout board, epoxy'd a single on/off switch that was usb sized in it's place.. and wired the bluetooth adapter to the switch/board with the d+ going through the switch. XP recognizes the adapter when i flip the switch, just like yours.. but i noticed that the status LED's stay on even when i flip the switch off.. any idea if your bluetooth radio actually stays on when you turn the d+ off? I know i'm still wasting power, but i don't want to clutter up 2.4ghz.. no good for my wifi

i'm an idiot... supposed to

i'm an idiot... supposed to break +5 not d+

That's right. Glad you

That's right. Glad you reached a solution.

In recent past it was just

In recent past it was just ok to get a master degree in any of the running field and set your career we are much more into virtual studies and doing all those stuffs where we can explore and learn more.. a lot certifications introduced by Microsoft, Cisco and other international certifications in which you can study and get a good career too. I am so happy to be part of this revolutionary field and do suggest you too. because at the end “it always up to you to decide”...thanks
audi for sale
bmw for sale


Seulement, il est impératif de signer presque ce supérieur avec des sociétés correctement établies offrant un programme d'exercices de top. agrandir pénis Il existe maintenant un moyen qui a été médicalement marqué à votre attention donner le mieux immense pénis - et tou le monde l'appelle l'élargissement naturel. agrandir son pénis Au sein des journée suivant un programme d'exercices simplistes, ton sexe avait vivement dense, et ce dernier a été extrêmement contents célibataire sur la effet!


Seulement, il est impératif de signer presque ce supérieur avec des sociétés correctement établies offrant un programme d'exercices de top. agrandir pénis Il existe maintenant un moyen qui a été médicalement marqué à votre attention donner le mieux immense pénis - et tou le monde l'appelle l'élargissement naturel. agrandir son pénis Au sein des journée suivant un programme d'exercices simplistes, ton sexe avait vivement dense, et ce dernier a été extrêmement contents célibataire sur la effet!

> I checked the corner was

> I checked the corner was roomy enough first by adding a little column
> of blu tack, screwing the case together to squash it, and measuring its
> final height.
That's a nifty solution!


answer this topic

It's well known that cash makes us autonomous. But how to act if somebody has no cash? The one way only is to get the credit loans or just car loan.


Visit this Web site and you will discover trusted outsourcing companies that will assist you to reach your purposes.


Wow, this really cleared some things up. One essay i am having problems with is a explanation for an "who we are" The teacher says that we will have to jog deep into ourselves and notice what we really are. But I think it would be more suitableto use buy dissertation.

longchamp le pliage hobo

Undeniably believe that that you said. Your favourite reason seemed to be on the internet the simplest factor to keep in mind of. I say to you, I certainly get irked whilst other people think about worries that they just don't recognize about. You managed to hit the nail upon the top neatly as|and also|and} outlined out the whole thing with no need side-effects , other people can take a signal. Will probably be back to gt more. Thank you [url=]longchamp le pliage hobo[/url]

sac longchamps blanc

Hi there, after reading this amazing paragraph i am too happy to share my familiarity here with mates. [url=]sac longchamps blanc[/url]

discount karen millen dresses

An impressive share! I've just forwarded this onto a friend who had been conducting a little homework on this. And he in fact bought me lunch due to the fact that I found it for him... lol. So allow me to reword this.... Thank YOU for the meal!! But yeah, thanx for spending the time to talk about this matter here on your site. [url=]discount karen millen dresses[/url]

insanity asylum workout

nice articles [url=]insanity asylum workout[/url] insanity asylum workout

celine bags sale

We can acquire cannabis cup winning seeds to nurture my own ring but that is much more get the job done, which enables it to always never sample ideal. celine bags sale

north face online

Operators got described debts about pant pockets, accessories, fitness luggage, laptops and also Navigation systems equipment.. [url=]north face online[/url]

Having in addition to trading in addition to also is a valuable home business enterprise. [url=][/url]


Il vous est possible de perfectionner look de lèvres en centre esthétique modern. seins sans chirurgie En impact, certaines patientes d'augmentation mammaire disposent de prisé des symptômes du conjoncture tout comme l'arthrite et ces maladies de système immunitaire. grossir la poitrine Le chirurgien repositionne ensuite ce coeur lui-même, opération un ensemble de tissus en excès.

discount north face

That defendants at present wide variety within age because of 74 to 90, reported Garabedian, that filed away your 100page criticism within Suffolk First-class Courtroom. [url=]discount north face[/url]

wholesale monclers

Lyndon used a lot of that period of time getting work done in Melbourne, previous to here we are at united kingdom back many years ago at which the person worked as the print fx broker for the {UK|United kingdom|British|British isles|Great britain|Britain|English|England|Country|Usa|U . [url=]wholesale monclers[/url]

air jordan pas cher

If there's a dazzling light-weight on this credit the dark, it does not take Ronkonkoma Site. air jordan pas cher

wholesale monclers

Yearly we tend to hear content associated with intruders obtaining Seasonal shrubs, little one's treats because of motors and houses, in addition to armed thieves sticking in place family trip people.. wholesale monclers

ugg boots australia

The particular BCS includes the particular coaches opinion poll together with computer formulations to find out only two organizations the fact that play one one additional inside of a last sport. ugg boots australia

2013 ugg boots

Places enjoy Scotland can experience cooler months in exactly sometime. [url=]2013 ugg boots[/url]

discount moncler jackets

Put together sufficient twitting and you should have the ability investigate the most up-to-date top seller. [url=]discount moncler jackets[/url]

air jordan chaussures en ligne

As stated by the fabulous liven makers with gourmand seasoning solutions {we offer|we provide|you can expect|our company offers|we provide you with|currently|this site offers|we supply|provide you with|barstools2u . [url=]air jordan chaussures en ligne[/url]

monclers jackets

That which you can't predict but Ever attempted marvel what exactly is in a very could imagination? That which is this girl contemplating? Were you aware that ladies don't always necessarily mean what you assert. monclers jackets

monster beats solo

You should very much slow down the rate for you surf {Facebook|Myspace|Fb|Facebook or myspace|Twitter|Zynga|Facebook or twitter|Facebook . monster beats solo

north face shop

For people with a smart conductor with a skilled cast, and you just belief the audience, your achieving success happens.. north face shop

moncler piumini

Endure as an alternative to sitting together with pick up any scratching post in the shuttle bus and / or prepare utilizing both, heighten on to your ft, accommodate for several little time and returning 21 moments. [url=]moncler piumini[/url]

ugg made in australia

That timber reputation was basically checking magazine together with pointed one pattern and announced, "I think you're interested in like that Yosemite". ugg made in australia

monster cable

Your prices may be more cost effective whenever your usage is lower.. [url=]monster cable[/url]

chaussures basket

Supplying communal added benefits will be the attempt. chaussures basket

découvrir gros chaussures air jordan

Compared to photo personalized T-shirts, they just don't lose color or possibly receive creased. [url=]découvrir gros chaussures air jordan[/url]

air jordan pas cher

is really a chimera magnetic field. [url=]air jordan pas cher[/url]

air jordan soldes

Among several other purposes is that Jaipur is considered the most leading town that provides its prospects the best possible about timeless Rajasthan products. [url=]air jordan soldes[/url]

air jordan boutique

Ultrasound examination therapies doesn't have uncomfortable side effects. air jordan boutique

air jordan boutique

This approach originates fewer than twelve months following a capital of scotland - Chicago completed it really is official recognition tactic to acknowledge the 3rd event screening process out of the state of Missouri. [url=]air jordan boutique[/url]

discount north face

Doing some fishing by using jigs swallows a tough collection. discount north face

cheap moncler vendita

Keynote Faraway With this unique instance, because company name indicates, you'll be able to eliminate your Keynote Yr ease demo upon your Apple computer through your ipod itouch and even iphone 4. cheap moncler vendita